Pump rotor for a canned motor pump

ABSTRACT

The invention relates to a pump rotor ( 26 ) for a canned motor pump. The pump rotor ( 26 ) comprises a base body ( 32 ) designed in one piece, with an impeller base disk ( 34 ) and a rotor holder bushing ( 36 ) and a rotor unit ( 40 ) with rotor magnets that are arranged on the rotor holder bushing ( 36 ).

TECHNICAL FIELD

The present invention relates to a pump rotor, particularly for a canned motor pump, in which a can is used.

STATE OF THE ART

Conventional canned motor pumps for pumping fluids, as they are used, for example, in the cooling system of a motor vehicle, have an impeller which is disposed on a shaft. An electric motor serves to drive the impeller. The rotor unit thereof is disposed on the same shaft as the impeller in order to avoid a complex gearing arrangement and is likewise exposed to the fluid to be pumped. In order to protect the stator and the control electronics of the electric motor from the fluid, a can sealed at the motor housing is provided between the rotor unit and the stator.

A canned motor pump of this kind is known, for example, from the European patent 1 281 870 A2 or from the American patent U.S. Pat. No. 7,704,019 B2. In the case of these known pumps, the impeller and a sleeve for receiving and for sealing the rotor unit are embodied in each case as separate parts, which in each case are connectable by means of a common hollow shaft.

It is hereby difficult to minimize the balance error of the pump rotors of conventional canned motor pumps of this kind This is the case on account of manufacturing and assembly tolerances, which only allow for the impeller as well as the rotor unit to be positioned on the shaft with limited precision.

It is the aim of the present invention to further develop a conventional canned motor pump in such a manner that a reduced balance error and consequently reduced wear of the pump rotor can be provided and furthermore that the manufacture of the pump rotor can be simplified.

This aim is met by a pump rotor according to claim 1.

SUMMARY

In order to meet said aim, the present invention provides a pump rotor for a canned motor pump, the pump rotor thereby comprising a base body designed in one piece, with an impeller base disk and a rotor holder bushing and a rotor unit with rotor magnets that are arranged on the rotor holder bushing.

As a result of the impeller base disk in the pump rotor according to the invention being integrally disposed with the rotor holder bushing for receiving the rotor unit, the positioning of the impeller and the rotor unit relative to the hollow shaft, which is common to both parts, can occur with greater accuracy than in a conventional pump rotor for a canned motor pump. In so doing the pump rotor according to the invention has a smaller mass offset in the radial direction between the blade part, the shaft and the rotor unit and consequently the balance error of said pump rotor is considerably less. Particularly by providing the impeller base disk on the base body, it is hereby especially easy to position the blade part exactly on the impeller base disk and thereby to minimize the balance error of the pump rotor according to the invention.

Furthermore, the manufacture of the pump rotor according to the invention is simplified as a result, and the wear on a canned motor pump having a pump rotor according to the invention can be reduced in relation to a conventional canned motor pump. Moreover, the noise generation of the pump rotor is reduced during operation, particularly the structure-borne sound of the first order and the harmonics thereof

Provision can be made in a first embodiment of the present invention for a receiving sleeve for the rotor unit to be integrally embodied with the base body. The rotor unit can be especially accurately positioned by such a receiving sleeve, and the balance error of the pump rotor can thereby be further reduced.

In doing so, a cover for the gastight sealing of the rotor unit can be provided, which is welded to the base body or injection molded onto said body. Particularly if the cover is welded to the receiving sleeve or injection molded onto said sleeve, a reliable sealing of the rotor unit from the fluid to be pumped can be achieved in a particularly simple manner.

In order to achieve a reliable transmission of torque between the rotor unit and the base body with the receiving sleeve for the rotor unit, provision can be made for the receiving sleeve and the rotor unit to be positively or non-positively coupled to one another. This coupling can comprise an engagement means between axial or radial interior surfaces of the receiving sleeve and axial or radial exterior surfaces of the rotor unit. A surface running obliquely to the radial direction can be provided on an interior surface of the receiving sleeve and on a corresponding exterior sleeve of the rotor unit, or the receiving sleeve and the rotor unit can be coupled to one another by friction contact.

In a second embodiment of the present invention, provision can be made for the rotor unit with the rotor magnets to be overmolded with plastic and fitted on the rotor holder bushing. In so doing, the rotor unit can be especially reliably sealed so as to be impermeable to fluids and gas by completely overmolding its exterior surfaces with plastic while an exact positioning of the rotor unit is still made possible by the rotor holder bushing, which is integrally provided with the impeller base disk on the pump rotor; and the balance error of the pump rotor can therefore be further kept to a minimum.

In the case of this second embodiment, a collar, which can be welded to the base body, can be provided on the overmolded rotor unit. In so doing, the rotor unit can be simply and precisely positioned on and attached to the base body, and the sealing off of the rotor unit from the fluid to be pumped can be further improved.

Provision can be made with regard to the inventive pump rotor according to the first or the second embodiment for a blade part to be connectable to the impeller base disk using rivet spigots, particularly by means of hot stamping or ultrasonic welding. In so doing, the blade part can be especially precisely and reliably positioned on and attached to the impeller base disk so that the error balance of the pump rotor can be minimized. In addition an especially simple assembly of the blade part and the base body is thereby made possible.

Provision can furthermore be made with regard to the pump rotor according to the invention for a bearing bushing for supporting the pump rotor to be disposed on a shaft radially inside of the rotor holder bushing. In so doing, a stable, low-wear mounting of the pump rotor can be achieved without the entire base body having to be manufactured from a material with appropriate properties.

The base body can thereby be configured as a plastic injection molded part, the bearing bushing being provided as an overmolded insert in the base body so that a stable mounting of the pump rotor on the shaft can also be achieved with a base body cost effectively manufactured from plastic.

BRIEF DESCRIPTION OF THE DRAWINGS

A preferred embodiment of the present invention is described below by way of example with the aid of the accompanying drawings.

FIG. 1 shows a cross-sectional view of a canned motor pump having a pump rotor according to a first embodiment of the present invention.

FIG. 2 shows a cross-sectional view of the pump rotor of FIG. 1.

FIG. 3 a shows the base body of the pump rotor of FIG. 1.

FIG. 3 b shows the assembly of the base body and of the rotor unit of the pump rotor of FIG. 1.

FIG. 4 shows a cross-sectional view of a pump rotor according to a second embodiment of the present invention.

FIG. 5 shows the assembly of the base body and of the rotor unit of the pump rotor of FIG. 4.

DETAILED DESCRIPTION

A first embodiment of the present invention is depicted in FIGS. 1 to 3 b. As can be seen in FIG. 1, a canned motor pump 10 comprises inlet and outlet channels 12, 14 for the fluid to be pumped, as for example coolant in the cooling circuit of an internal combustion engine; and a motor housing 16 is configured such that it is divided by a can 18 into a dry space 20 and a wet space 22, which are in each case sealed against each other.

The stator 24 and the control electronics for the electric motor for driving the pump are disposed in the dry space 20. In the wet space 22, the pump rotor 26 is rotatably mounted on a shaft 30, which is fixedly attached in the motor housing 16, by means of a bearing bushing 28.

The pump rotor 26 comprises a base body 32 designed in one piece, with an impeller base disk 34, a rotor holder bushing 36 and a receiving sleeve 38 for receiving a rotor unit 40. The open side of the receiving sleeve 38 is closed with a cover 42. A blade part 44 is attached to the impeller base disk 34 and together with said impeller base disk 34 forms an impeller. As can be seen in FIG. 2, the blade part 44 is attached to the impeller base disk 34 using rivet spigots 46, which are connected to said impeller base disk 34 by means of hot stamping or ultrasonic welding.

As is depicted in FIG. 3 a, the base body 32 is initially provided, which is manufactured as a plastic injection molded part having the bearing bushing 28 as an overmolded insert. The impeller base disk 34, the rotor holder bushing 36 and the receiving sleeve 38 are integrally provided on the base body 32. The rotor unit 40, which is configured in a fundamentally known manner as a laminated core with preassembled rotor magnets, is then inserted into the receiving sleeve 38, as shown in FIG. 3 b.

An engagement means, an oblique surface or the like, is thereby provided in each case on an exterior surface of the rotor unit 40 and on a corresponding interior surface of the receiving sleeve 38. In so doing, the transmission of torque from the rotor unit 40 to the base body 32 (and therefore to the blade part 44 of the pump rotor 26) is assured by a positive interlock between the rotor unit 40 and the receiving sleeve 38. The transmission of torque between the rotor unit 40 and the blade part 44 can also alternatively occur via a frictionally engaged connection between the rotor unit 40 and the receiving sleeve 38.

As a result of the receiving sleeve 38 being manufactured as an injection molded part integrally with the base body 32, the rotor unit 40 of the pump rotor 26 can be positioned with particularly great accuracy according to the first embodiment of the present invention. In so doing, the radial mass offset between the rotor unit 40 and the base body 32 and thus the resulting balance error of the pump rotor are very slight.

After inserting the rotor unit 40, the open end of the receiving sleeve 38 is closed with the cover 42 in a gastight manner. The cover 42 can be welded to the receiving sleeve 38 by means of friction welding, ultrasonic welding or laser welding or can be injection molded thereto. The rotor unit 40 with the rotor magnets is thereby reliably sealed off from the fluid to be pumped although said unit 40 is situated in the wet space 22 of the canned motor pump 10.

Finally, as described above, the blade part 44 is attached by means of rivet spigots 46 to the base body 32, which has already been provided with the rotor unit 40. Because of the fact that the blade part 44 is attached to the large-surface impeller base disk 34 using a plurality of rivet spigots 46, the blade part 44 can be especially precisely positioned on the base body 32, and the mass offset between the blade part 44 and the base body 32 with the rotor unit 40 can be minimized without much effort or expense.

The pump rotor 26 according to the first embodiment of the present invention can therefore be especially easily provided and with a reduced error balance in relation to conventional pump rotors for canned motor pumps.

A second embodiment of the present invention is depicted in FIG. 4 and FIG. 5. The basic design of a canned motor pump, in which the pump rotor 126 is used according to the second embodiment, is not different from the design of the canned motor pump 10 for the pump rotor 26 according to the first embodiment of the present invention, which is depicted in FIG. 1.

As is depicted in FIGS. 4 and 5, the base body 132 of the pump rotor 126 according to the second embodiment of the present invention is manufactured as a plastic injection molded part having the bearing bushing 128 as an overmolded insert and comprises an impeller base disc 134 and a rotor holder bushing 136. A projection 148, with which the positioning of the rotor unit 140 can be defined in the axial direction, is provided on the base body 132 in the region of the rotor holder bushing 136.

The rotor unit 140 comprises a laminated core with preassembled rotor magnets and is overmolded such that the resulting pre-molded part 150 completely surrounds the rotor unit 140 at its exterior surfaces, the inside diameter of the rotor unit 140 remaining free. A peripheral collar 152, which is integrally configured with the pre-molded part 150, is in each case injection molded onto the axial ends of said pre-molded part 150. In so doing, said peripheral collar 152 is embodied having an excessive interference fit with respect to the rotor holder bushing 136 of the base body 132.

If the pre-molded part 150 surrounding the rotor unit 140 and having the two peripheral collars 152, is fitted onto the base body 132, a certain amount of sealing also of the inside diameter of the rotor unit 140 with respect to the fluid to be pumped as well as a friction closure between the rotor unit 140 and the rotor holder bushing 136 is consequently already provided for the transmission of torque between the rotor unit 140 and the blade part 144 by the collars 152, which are embodied having an excessive interference fit with respect to the rotor holder bushing 36. By the two collars 152 being welded to the base body 132 by means of laser radiation welding, the joining pressure being generated by the prestressing due to deformation, the sealing of the rotor unit 140 as well as the transmission of torque between the rotor unit 140 and the blade part 144 are even further improved.

Finally in order to provide the pump rotor 126 according to the second embodiment of the present invention, the blade part 144 is still attached to the impeller base disk 134 of the base body 132 as described in connection with the first embodiment.

The pump rotor 126 according to the second embodiment of the present invention therefore also has a reduced balance error when compared with conventional pump rotors and can be especially easily assembled. 

1. Pump rotor for a canned motor pump, comprising: a base body designed in one piece, with an impeller base disk and a rotor holder bushing and a rotor unit with rotor magnets that are arranged on the rotor holder bushing.
 2. Pump rotor according to claim 1, wherein that the invention provides a receiving sleeve integrally embodied with the base body for the rotor unit.
 3. Pump rotor according to claim 2, wherein the invention provides a cover for the gastight closure of the rotor unit, said cover particularly being welded or injection molded to the base body.
 4. Pump rotor according to claim 2, wherein the receiving sleeve and the rotor unit are positively or non-positively coupled to one another in order to cause a transmission of torque between the rotor unit and the base body.
 5. Pump rotor according to claim 1, wherein the rotor unit with the rotor magnets is overmolded with plastic and fitted on the rotor holder bushing.
 6. Pump rotor according to claim 5, wherein a collar, which can be welded to the base body, is provided on the overmolded rotor unit.
 7. Pump rotor according to claim 1, wherein a blade part is connected to the impeller base disk of the base body using rivet spigots, particularly by means of hot stamping or ultrasonic welding.
 8. Pump rotor according to claim 1, wherein a bearing bushing for supporting the pump rotor is disposed on a shaft radially inside of the rotor holder bushing.
 9. Pump rotor according to claim 8, wherein the base body is configured as a plastic injection molded part, the bearing bushing being provided as an overmolded insert in the base body. 